Characteristics of unturned eggs: critical period, retarded embryonic growth and poor albumen utilisation.

1. The physiological effects of egg turning during incubation are described. 2. There was a critical period for turning, from days 3 to 7 of incubation, which affected hatchability, embryo growth and utilisation of extra-embryonic fluids. 3. Failure to turn eggs retarded formation of allantoic and amniotic fluids, restricted alumen uptake and retarded growth of the embryo, but only after day 12 of incubation.